This invention relates to a process for the treatment of a filament cable in an apparatus into which it is introduced and in which it is treated and from which it is carried out, and to the apparatus itself.
Filament cables are generally subjected to various treatments such as drying, relaxation and thermo-setting, especially after they have been washed, stretched or scrooped, for example in order that they may acquire a certain moisture content and certain properties such as elongation, strength or dye absorption. In addition, such filament cables are normally crimped in order to prevent their falling apart into individual filaments and/or in order to ensure, in the case of staple fibres, that they will adhere sufficiently firmly to one another for the subsequent spinning process. The various treatments such as drying, relaxation and thermo-setting are normally carried out by treating the filament cable with a gas, in particular with steam or heated air. These steam treatments and drying processes require certain residence times to be observed.
In conventional after-treatment processes carried out at low production rates of up to 150 m/min and with heavy filament cables, for example of 100 ktex, the requisite residence times are obtained by using screen drum driers comprising a series of screen drums, for example 20 to 30 drums each having a diameter of 140 cm. Drying is carried out with heated air which must flow at a rate of 3 to 5 m/sek if sufficient drying is to be achieved. The energy requirement for this is considerable. Since residues of solvent or of monomer are invariably expelled from the filament cable during the steam treatment or dying, it is necessary to insulate the drying apparatus from the surroundings, but this can only be incompletely achieved in the case of a screen drum drier. Crimping is generally carried out after drying.
As an alternative, so called screen belt driers are known, on which the product is deposited along a meandering line and with little tension and is transported in this form through the treatment zones. The low tension, in fact in most cases tension free deposition of the material on the screen belt has the disadvantage that the layers of folded cable which are the first to be deposited lie at the bottom and are progressively covered by layers of products subsequently deposited so that when the cable is drawn off the screen belt a large part of the cable has to be pulled out from under the rest of the cable. This may lead to entanglement of the layers and felting which may interfere with the smooth running of the process. To overcome this disadvantage, the cable must be deposited on so called turning drums before its introduction into the steam treatment or drying apparatus so as to ensure that when the cable is deposited on the screen belt, those layers which are laid down first will come to lie at the top and can easily be drawn off.
One disadvantage of this complicated technique is that the apparatus is difficult to seal off at the product inlet end, with the result that large quantities of excess air are drawn into the apparatus and are unnecessarily heated up and may impair the purity of the treatment gas, and harmful substances are liable to escape through the leakages. There is the further disadvantage that the turning drum cools the cable and thereby entails an energy loss.
For the steam treatment/relaxation of staple fibre/flock, it is known to use screen belt steamers in which the material together with a relatively large quantity of air is introduced into the treatment zone by means of the screen belt and is steamed in this zone by the circulation of super heated steam. The disadvantages of this apparatus lie in the difficulty of sealing it off combined with the indefinite steam concentrations and the large amount of time required, for example when a colour change is carried out.